Despite the growing importance of multicastdependent network services, the support of multicast traffic still remains far from satisfactory in currentgeneration switches and routers. In this paper, we propose a practical and tractable switching architecture to efficiently support multicast traffic while only requiring one redundant multicast module. We call the resulting scheme as Combined Input Separate Output Queued switch (CISOQ for short). Furthermore, we prove that 100% throughput can be achieved by a CISOQ switch as long as the multicast traffic load satisfies the assumptions that it is multicast-admissible and SLLN and that it dose not oversubscribe any inputs or outputs. To the best of our knowledge, we are not aware of any analytical studies of multicast traffic arrival process prior to this work.